Dye sensitized solar cell

ABSTRACT

A dye-sensitized solar cell that includes a semiconductor layer, to which a photosensitive dye generating electrons is adhered; a photo electrode disposed on a side of the semiconductor layer so as to transfer electrons; and an auxiliary electrode disposed on the other side of the semiconductor layer so as to transfer the electrons, and at least one semiconductor layer and at least one auxiliary electrode are stacked alternatively. Thus, an amount of molecules of the photosensitive dye may be increased without increasing the moving distance of electrons, and the efficiency of the solar cell may be increased.

RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No.10-2009-0117836, filed on Dec. 1, 2009, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

1. Field

The general inventive concept relates to a dye sensitized solar cell.

2. Description of the Related Art

The above information disclosed in this Related Art section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known to a person of ordinary skill in the art.

SUMMARY

Aspects of the present invention include an improved dye-sensitizedsolar cell which may increase the amount of dye molecules whilepreventing the moving distance of electrons from increasing.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to exemplary embodiments of the present invention, adye-sensitized solar cell may be fabricated with a semiconductor layer,to which a photosensitive dye generating electrons is adhered; a photoelectrode disposed on a side of the semiconductor layer so as totransfer the electrons; and an auxiliary electrode disposed on the otherside of the semiconductor layer so as to transfer the electrons. Atleast one semiconductor layer and at least one auxiliary electrode arestacked alternatively.

The dye-sensitized solar cell may further include an electrolyte forreducing the photosensitive dye, and the auxiliary electrode may includea plurality of holes, through which the electrolyte is transmitted.

The dye-sensitized solar cell may further include a counter electrode towhich the electrons are moved via an external circuit from the photoelectrode. The counter electrode may further include a catalyst layerfor accelerating the reduction of the electrolyte. The dye-sensitizedsolar cell may further include glass layers disposed on an outer portionof the photo electrode and an outer portion of the counter electrode.

The semiconductor layer may be formed of titanium dioxide (TiO₂), theauxiliary electrode is formed of Ti, and the photo electrode is formedof fluorine-doted tin oxide (FTO).

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of these and other aspects, and many of theattendant advantages thereof, will be readily apparent as the samebecomes better understood by reference to the following detaileddescription when considered in conjunction with the accompanyingdrawings in which like reference symbols indicate the same or similarcomponents, wherein:

FIG. 1 is a cross-sectional view of a dye-sensitized solar cellaccording to an embodiment of the present invention; and

FIG. 2 is a cross-sectional view of a dye-sensitized solar cellaccording to another embodiment of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings, wherein like referencenumerals refer to the like elements throughout. In this regard, thepresent embodiments may have different forms and should not be construedas being limited to the descriptions set forth herein. Accordingly, theembodiments are merely described below, by referring to the figures, toexplain aspects of the present description.

Recognizing that sizes and thicknesses of constituent members shown inthe accompanying drawings are arbitrarily given for better understandingand ease of description, the present invention is not limited to theillustrated sizes and thicknesses.

In the drawings, the thickness of layers, films, panels, regions, etc.,are exaggerated for clarity. Like reference numerals designate likeelements throughout the specification. It will be understood that whenan element such as a layer, film, region, or substrate is referred to asbeing “on” another element, it can be directly on the other element orintervening elements may also be present. Alternatively, when an elementis referred to as being “directly on” another element, there are nointervening elements present.

In order to clarify the present invention, elements extrinsic to thedescription are omitted from the details of this description, and likereference numerals refer to like elements throughout the specification.

In general, dye sensitized solar cells use photosensitive dye thatgenerates electron-hole pairs by absorbing solar energy of visible rays.The photosensitive dye may be adhered on a metal oxide semiconductorlayer such as titanium dioxide (TiO₂). When solar light is absorbed bythe photosensitive dye, molecules of the photosensitive dye aretransited from a base state to an excited state to generateelectron-hole pairs, and the excited electrons are injected into aconduction band of the semiconductor layer and moved to an adjacentelectrode, that is, a photo electrode. Then, the excited electrons aremoved to a counter electrode, that is, a positive electrode, via anexternal circuit. In addition, molecules of the dye which are oxidizedby the transition of electrons are reduced in an electrolyte, andelectrolytic ion oxidized by the reduction of dye molecules is reducedby reaction with electrons that have reached a counter electrode.

As described above, dye-sensitized solar cell performs as a batterybasically by inducing generation, transition, and reduction of electronscaused by the photosensitive dye absorbing solar light.

Therefore, when the amount of generated electrons is increased, thehigher the efficiency of the dye-sensitized solar cell. To accomplishthis the semiconductor layer may be made thicker in order to increase anamount of the photosensitive dye adhering to the semiconductor layer.However, when the semiconductor layer becomes thicker, the movingdistance of the electrons which moves to the photo electrode is alsoincreased. Thus, the efficiency of the solar cell may be degraded.

Therefore, in order to improve the efficiency of the solar cell, anappropriate structure that may increase the amount of the photosensitivedye while reducing the moving distance of electrons is required.

FIG. 1 is a cross-sectional view of a dye-sensitized solar cellaccording to an embodiment of the present invention. Referring to FIG.1, the dye-sensitized solar cell of this embodiment includes asemiconductor layer 10 to which a photosensitive dye is adhered, a photoelectrode 20 and an auxiliary electrode 30 disposed to contact a sideand the other side of the semiconductor layer 10, and a counterelectrode 40 connecting to the photo electrode 20 via an externalcircuit (not shown).

End portions of the photo electrode 20 and the auxiliary electrode 30are electrically connected to each other so that electrons generated inthe semiconductor layer 10 may freely move therethrough. Therefore,electrons generated in the semiconductor layer 10 may move to any of thephoto electrode 20 and the auxiliary electrode 30, and then, theelectrons may move toward the counter electrode 40 via the externalcircuit that is connected to the photo electrode 20. That is, the photoelectrode 20 and the auxiliary electrode 30 may perform as a negativeelectrode surrounding the semiconductor layer 10. Then, even when thesemiconductor layer 10 is made thicker, for example, twice the originalthickness of the semiconductor layer 10, the moving distance of theelectrons in the semiconductor layer 10 rarely changes. That is, thephoto electrode contacts only a side of the semiconductor layer in theconventional dye-sensitized solar cell, and thus, when the thickness ofthe semiconductor layer is increased, the distance for the electronsgenerated on a portion apart from the photo electrode to reach the photoelectrode 20 across the inside of the semiconductor layer is alsoincreased. However, when the photo electrode 20 and the auxiliaryelectrode 30 surround the semiconductor layer 10, as in this embodiment,the electrons generated in the semiconductor layer 10 may move to any ofthe photo electrode 20 and the auxiliary electrode 30 surrounding thesemiconductor layer 10, and thus, the moving distance of the electronsdoes not increase even if the thickness of the semiconductor layer 10doubles. Here, the semiconductor layer 10 may be formed of TiO₂, thephoto electrode 20 may be formed of fluorine doped tin oxide (FTO), andthe auxiliary electrode 30 may be formed of Ti.

In addition, the dye-sensitized solar cell of this embodiment includesthe structure, in which the semiconductor layer 10 and the auxiliaryelectrode 30 are repeatedly stacked. As described above, the amount ofphotosensitive dye adhered on the semiconductor layer 10 may beincreased by increasing the thickness of one semiconductor layer 10.However, multiple semiconductor layers 10 may be stacked in order toincrease the adhered amount of the photosensitive dye even more.

Reference numeral 50 denotes an electrolyte, which reduces thephotosensitive dye molecules that are oxidized by the generation ofelectrons. Since the electrolyte 50 contacts the semiconductor layer 10in order to generate the reduction, the auxiliary electrode 30 mayinclude a plurality of holes 31, through which the electrolyte 50 aretransmitted. In addition, since the semiconductor layer 10 is a porousoxide semiconductor, the semiconductor layer 10 may transmit theelectrolyte 50 without using holes. Therefore, the electrolyte 50 maycontact the multiple semiconductor layers 10 to generate the reduction.

Reference numeral 60 denotes a platinum catalyst layer for acceleratingthe reduction reaction of the electrolyte 50. That is, the electrolyte50 is oxidized according to the reduction of the semiconductor layer 10,and then, the electrolyte 50 is reduced by the reaction with theelectrons which have reached the counter electrode 40 from the photoelectrode 20. The catalyst layer 60 accelerates the reduction.

Reference numerals 70 and 80 denote glass layers which are installedoutside of the photo electrode 20 and the counter electrode 40 in orderto protect internal elements. Reference numeral 90 denotes a sealingmember for sealing the electrolyte 50.

The dye-sensitized solar cell having the above structure operates asfollows.

When solar light is irradiated onto the solar cell, molecules of thephotosensitive dye adhered on the semiconductor layer 10 absorb thesolar energy of visible ray area to generate electrons. Here, thegenerated electrons move to the photo electrode 20 or the auxiliaryelectrode 30 which surround the semiconductor layer 10. In addition, theelectrons move to the counter electrode 40 via the external circuit (notshown) connected to the photo electrode 20, and then, a load may beconnected to the external circuit to use the solar cell.

In addition, the molecules of the photosensitive dye which are oxidizedby the generation of electrons are reduced by the reaction with theelectrolyte 50, and the electrolyte 50 which is oxidized due to thereduction of the photosensitive dye molecules is reduced by the reactionwith the electrons that have reached the counter electrode 40.

The solar cell is operated by the above circulation mechanism ofelectrons, and the generated amount of electrons is increased much morethan that of the conventional solar cell. That is, as described above,the thickness of the semiconductor layer 10 may be increased byadditionally forming the auxiliary electrode 30, and thus, adhesionamount of the photosensitive dye may be increased. Furthermore, multiplesemiconductor layers 10 are stacked, and thus, the molecules of thephotosensitive dye generating the electrons are greatly increased. Whenthe generated amount of electrons is increased, the electronstransferring through the external circuit also increase, and then, theefficiency of the solar cell is improved. In addition, as describedabove, the moving distance of the electrons 10 transmitting through thesemiconductor layer 10 to the photo electrode 20 or the auxiliaryelectrode 30 does not increase.

On the other hand, two semiconductor layers 10 are stacked in thisembodiment, however, three or more semiconductor layers 10 may bestacked as shown in FIG. 2.

Therefore, according to the dye-sensitized solar cell having the abovedescribed structure, the amount of photosensitive dye molecules isgreatly increased without increasing the moving distance of theelectrons, and thus, the cell efficiency may be improved.

It should be understood that the exemplary embodiments described thereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments.

1. A dye-sensitized solar cell comprising: a semiconductor layer, towhich a photosensitive dye generating electrons is adhered; a photoelectrode disposed on a side of the semiconductor layer so as totransfer the electrons; and an auxiliary electrode disposed on anotherside of the semiconductor layer so as to transfer the electrons; whereinat least one semiconductor layer and at least one auxiliary electrodeare stacked alternatively.
 2. The dye-sensitized solar cell of claim 1,further comprising an electrolyte for reducing the photosensitive dye,wherein the auxiliary electrode includes a plurality of holes, throughwhich the electrolyte is transmitted.
 3. The dye-sensitized solar cellof claim 2, further comprising a counter electrode to which theelectrons are moved via an external circuit from the photo electrode. 4.The dye-sensitized solar cell of claim 3, wherein the counter electrodefurther include a catalyst layer for accelerating the reduction of theelectrolyte.
 5. The dye-sensitized solar cell of claim 4, furthercomprising glass layers disposed on an outer portion of the photoelectrode and an outer portion of the counter electrode.
 6. Thedye-sensitized solar cell of claim 1, wherein the semiconductor layer isformed of titanium dioxide (TiO₂), the auxiliary electrode is formed ofTi, and the photo electrode is formed of fluorine-doted tin oxide (PTO).7. A dye-sensitized solar cell comprising: a plurality of semiconductorlayers each having a rectangular shape with a top side, a bottom sideand two end sides; a photosensitive dye adhering to each of theplurality of semiconductor layers that generates electrons upon exposureto light; a photo electrode disposed on a bottom side of a singlesemiconductor layer of the plurality of semiconductor layers so as totransfer the electrons; and a plurality of auxiliary electrodes disposedon the top side and both end sides of each of the plurality ofsemiconductor layers so as to transfer the electrons; wherein eachsemiconductor layer of the plurality of semiconductor layers and eachauxiliary electrode of the plurality of auxiliary electrodes arealternately stacked.
 8. The dye-sensitized solar cell of claim 7,further comprising: an electrolyte for reducing the photosensitive dye,wherein the plurality of auxiliary electrodes include a plurality ofholes, through which the electrolyte is transmitted.
 9. Thedye-sensitized solar cell of claim 8, further comprising: a counterelectrode to which the electrons are moved via an external circuit fromthe photo electrode.
 10. The dye-sensitized solar cell of claim 9,wherein the counter electrode further comprises: a catalyst layer thataccelerates the reduction of the electrolyte.
 11. The dye-sensitizedsolar cell of claim 10, further comprising: glass layers disposed on anouter portion of the photo electrode and an outer portion of the counterelectrode.
 12. The dye-sensitized solar cell of claim 7, wherein theplurality of semiconductor layers is formed of titanium dioxide (TiO₂),the auxiliary electrode is formed of Ti, and the photo electrode isformed of fluorine-doted tin oxide (FTO).